The stations are complete, the tracks are finished and it’s in good enough shape to run test trains at 160 km/h.

But Victorians won’t be using the Regional Rail Link – a new rail line through Melbourne’s west started under John Brumby, largely funded by Canberra, and soon to be completed under Denis Napthine – for another six months.

Tarneit train station. Photo: Jason South

Originally proposed by then public transport minister Lynne Kosky in 2008, it is Melbourne’s first new major rail line in 80 years. It includes two new stations: Tarneit, and Wyndham Vale near Werribee.

Promised at a cost of $4.3 billion, the 44 kilometres of twin rail lines will be delivered for $4.1 billion.

It is now planned to formally open next April, when V/Line expects its next major timetable change to be released.

An aerial view of Tarneit station. Photo: Jason South

Public Transport Minister Terry Mulder put the project on hold for four months after winning office at the last state election, saying at the time there was a “massive budget black hole” left and the project was as much as $1.1 billion over budget.

Ultimately it has been delivered for nothing like what was feared, although it is running behind its completion date of December 2014 – rescheduled by Mr Mulder to 2016 to avoid any embarassments if the project ran over time.

The secrecy surrounding the project’s budget has been extraordinary, with even Auditor-General John Doyle unable to get accurate figures, expressing concern in his last annual report to Parliament.

The government authority behind the project, Mr Doyle wrote last year, was deliberately withholding budget information, and “inappropriately reducing its accountability to Parliament and to the public for project delivery and potential cost overruns”.

Mr Mulder said on Thursday that Labor had “left this project as a basket case”, and argued the government had been forced to put in extra money to get it back on track.

But Luba Grigorovitch, state secretary of the Rail, Tram and Bus Union, said the expected six-month wait before the rail line opened to the public showed the government “has never really been committed to the Regional Rail Link project”.

“When they came into government, they wasted valuable time deciding whether to proceed with the project,” she said. “They have been so focused on trying to convince people the East West Link is a good idea, regional rail hasn’t been their focus.”

A spokesman for the Regional Rail Link Authority, which the state government put in charge of the project in 2010, said there had been testing of the line’s new signalling systems over the past week.

V/Line driver training had also started this week, he said.

Labor’s public transport spokeswoman Jill Hennessy said the line’s expected opening date of next April showed the Napthine government’s claim of a 2016 opening “never had any basis – [the] government simply added a huge margin to cover any delays, and there were none”.